Harnisch et al., U.S. Pat. No. 4,841,052 issued Jun. 20, 1989 describe naphthalic acid imides useful as charge-regulating substances in electrophotographic toners.
Brana et al., U.S. Pat. No. 4,874,863 issued Oct. 17, 1989 discloses anticancer compounds of the formula: ##STR3## wherein X.sup.1, X.sup.2, X.sup.3 and X.sup.4 are identical or different and are each H, NO.sub.2, NH.sub.2, C.sub.1 -C.sub.6 -alkylamino, di-C.sub.1 -C.sub.6 -alkylamino, OH, C.sub.1 -C.sub.6 -alkoxy, halogen, trihalomethyl, C.sub.1 -C.sub.6 alkyl, formyl, C.sub.1 -C.sub.6 -alkylcarbonyl, ureyl, C.sub.1 -C.sub.6 -alkylureyl and R is a straight chain or branched C.sub.4 -C.sub.10 -alkylene which is interrupted at one or two points in the chain by a secondary or tertiary amino group, where 2 nitrogen atoms may additionally be bonded to one another by an alkylene group, or a salt with a physiologically tolerated acid.
Brana et al., U.S. Pat. No. 4,874,863 does not specifically disclose the compounds of the present invention.
The compounds of the present invention have unexpectedly increased water solubility compared to certain compounds specifically disclosed in U.S. Pat. No. 4,874,863. This is an important advantage, since the less soluble compounds present serious problems when trying to formulate such compounds into a dosage form suitable for human use.
In addition the compounds of the present invention exhibit unexpected superior antitumor activity relative to the compounds specifically disclosed by Brana et al.